Medtronic's 3-Year SYMPLICITY HTN-2 Data Published

June 4, 2014—The 36-month results from the SYMPLICITY HTN-2 trial were published by Murray D. Esler, MD, et al, online ahead of print in European Heart Journal. Catheter-based renal denervation using the Symplicity renal denervation system (Medtronic, Inc.) resulted in sustained lowering of blood pressure at 3 years in a selected population of subjects with severe, treatment-resistant hypertension without serious safety concerns, concluded the investigators.

In October 2013, Medtronic announced that Robert J. Whitbourn, MD, presented the 36-month data at the TCT 2013: Transcatheter Cardiovascular Therapeutics conference in San Francisco, California.

As summarized in European Heart Journal, the randomized SYMPLICITY HTN-2 clinical trial aimed to determine long-term results of renal artery denervation for patients with treatment-resistant hypertension. The trial randomized 106 patients to renal denervation or medical therapy alone. At 6 months, 37 control patients crossed over to renal denervation. Office blood pressure measurements, antihypertensive medication use, and safety events were followed every 6 months through 3 years.

Follow-up was available at 36 months for 40 of 52 patients in the initial renal denervation group and at 30 months for 30 of 37 patients who crossed over and received renal denervation at 6 months. Baseline blood pressure was 184 ± 19/99 ± 16 mm Hg in all treated patients. 

The investigators found that at 30 months after the procedure, systolic blood pressure decreased by 34 mm Hg (95% CI, -40, -27; P < .01), and diastolic blood pressure decreased by 13 mm Hg (95% CI, -16, -10; P < .01). The systolic and diastolic blood pressure reduction at 36 months for the initial renal denervation group was -33 mm Hg (95% CI, -40, -25; P < .01) and -14 mm Hg (95% CI, -17, -10; P < .01), respectively. 

Procedural complications included one hematoma and one renal artery dissection before energy delivery that was treated successfully. Later complications included two cases of acute renal failure, which fully resolved, 15 hypertensive events requiring hospitalization, and three deaths, reported the investigators in European Heart Journal.

As previously noted by Medtronic, the Symplicity renal denervation system treats uncontrolled hypertension by disrupting the output of hyperactive sympathetic nerves within the renal artery wall, which is central to the body’s ability to regulate blood pressure. The device consists of a flexible catheter and generator with algorithms developed to enhance the safety and effectiveness of the renal denervation procedure. The Symplicity system received European CE Mark approval in 2008. The Symplicity renal denervation system is available for investigational use only in the United States.

In March 2014, Medtronic announced that the full results of the SYMPLICITY HTN-3 clinical trial met the its primary safety endpoint but did not meet its primary or secondary efficacy endpoints. Based on these results, the company stated at that time that it was reassessing the future of the company's global renal denervation hypertension program.

The SYMPLICITY HTN-3 data were presented in a late-breaking session at the ACC.14: 63rd annual scientific sessions of the American College of Cardiology and published in The New England Journal of Medicine (2014;370:1393–1401).